AND measuring gives starting point and confirms that the expected changes actually occur.

Most of the literature says that a hard shifts point to high modulator pressure when vacuum is correct. It "seems" (to me) that VCV and modulator interact. I tried turning the modulator down without using a gauge. Perhaps I should have turned VCV up. Regardless, the modulator change didn't fix the shifting and I have no idea whether or not my turning the modulator T actually had an effect on modulator pressure.

Vacuum out of the pump has always been ~ 18' on my car with my gauge(s). It is less than that coming out of the orifice. I don't remember what the VCV pressure is but it does drop to 0.

Modulator pressure? I have no idea. It does (did the list time I measured) hold vacuum. The other vacuum systems except for the door locks are good. Door lock system is plugged with a bolt and is out of the shift system.

I'll go back and test pressures then measure what effect changes have. Now, I'm mostly flying blind. Will report back.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

You never stated the symptoms of your issue..........?

Although you believe you are "flying blind", I have a suspicion that you're flying in the wrong direction.

There are specific tests that you can make to put you on the correct path, even if accurate data points are not currently available.